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// Version 2 of unicorn, uses gif.GIF as store of pixels
// & a separate goroutine to render it so it can do
// animated GIFs
package unicorn
import (
"image"
"image/color/palette"
"image/gif"
"time"
)
// Unicorn2 ...
// Interface for interacting with the Unicorn HAT HD
// Implemented by both real & fake unicorns.
type Unicorn2 interface {
// Change the image
GetGif() *gif.GIF
SetGif(*gif.GIF)
// Starts the rendering goroutine
StartRender() chan bool
// Must be implemented to actually render the image to device
renderImage(image.Image)
// Required for os to not think we're stuck
MainLoop()
}
// BaseUnicorn2 ...
// Common to both real & fake unicorns!
// timing code for rendering & stopping rendering
type BaseUnicorn2 struct {
g *gif.GIF
}
func (u *BaseUnicorn2) GetGif() *gif.GIF {
return u.g
}
func (u *BaseUnicorn2) SetGif(g *gif.GIF) {
u.g = g
}
func NewBaseUnicorn2() *BaseUnicorn2 {
im := image.NewPaletted(
image.Rect(0, 0, 16, 16),
palette.WebSafe)
gf := &gif.GIF{
Image: []*image.Paletted{im},
Delay: []int{50},
Disposal: []byte{gif.DisposalBackground},
BackgroundIndex: 0, // This is black in the websafe palette
}
return &BaseUnicorn2{
g: gf,
}
}
// StartRenderBase ...
// Deals with the timing aspect of animated GIFs
func (u *BaseUnicorn2) StartRenderBase(renderImage func(image.Image)) chan bool {
stopChan := make(chan bool)
go func() {
timer := time.NewTimer(0)
imageIndex := 0
running := true
for running {
select {
case <-stopChan:
timer.Stop()
running = false
case <-timer.C:
gf := u.GetGif()
// Image could change underneath us, but there should always be 1 image at least.
if imageIndex >= len(gf.Image) {
imageIndex = 0
}
im := gf.Image[imageIndex]
delay := gf.Delay[imageIndex] //100ths of a second, 10^-2
renderImage(im)
timer.Reset(time.Duration(delay * 10000000)) // nanoseconds 10^-9 sec
imageIndex = (imageIndex + 1) % len(gf.Image)
}
}
}()
return stopChan
}
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